Light expanded clay aggregates for phosphorous removal

Abstract

Sintered light expanded clay aggregates are described that are prepared by expanding and firing a clay-based material, and where the finished aggregates have a diameter of up to about 32 mm, for use as filtration medium for purifying water, wherein carbonates of calcium and/or magnesium are added to the clay as flux material prior to expansion and firing. Uses of the expanded clay aggregates for removing phosphorous by utilising die clay aggregates are also described, as well as a method for removing phosphorus by using the clay aggregates.

What is claimed is:  
     
       1. A process for removing phosphorous from phosphorous-containing waste water, said process comprising the steps of: 
       a) mixing clay and carbonates selected from the group consisting of calcium carbonate, magnesium carbonate, and dolomite to form a mixture;  
       b) introducing the mixture into a rotary kiln to form pellets;  
       c) firing and expanding the pellets thereby producing a light expanded aggregate;  
       d) contacting the light expanded aggregate with the phosphorous-containing water;  
       wherein the light expanded aggregate has a capacity for adsorption of phosphorous of at least 4000 mg P/kg light expanded aggregate.  
     
     
       2. The process according to  claim 1 , wherein the carbonates are dolomite. 
     
     
       3. The process according to  claim 1 , wherein the light expanded clay aggregate has a diameter less than 32 mm. 
     
     
       4. The process according to  claim 3 , wherein the expanded clay aggregate is broken down to a particle size of less than 10 mm. 
     
     
       5. The process according to  claim 3 , wherein the expanded clay aggregate is broken down to a particle size of 1-4 mm. 
     
     
       6. The process according to  claim 1 , wherein the amount of the carbonate added is 5-50% by weight. 
     
     
       7. The process according to  claim 1 , wherein the amount of the carbonate added is 5-20% by weight. 
     
     
       8. The process according to  claim 2 , wherein the amount of the carbonate added is 5-50% by weight. 
     
     
       9. The process according to  claim 2 , wherein the amount of the carbonate added is 5-20% by weight. 
     
     
       10. The process according to  claim 1 , wherein the light expanded aggregate adsorbs at least 4000 mg P/kg light expanded aggregate. 
     
     
       11. The process according to  claim 1 , wherein the light expanded aggregate adsorbs at least 1500 mg P/kg light expanded aggregate.